1. A cable that is doubled back on itself such that two or more geophone stations are located at the same position on the ground. Used for making comparisons (for example, of different types of geophone arrays). 2. Frequencies greater than the Nyquist frequency are folded back, causing data to alias (q.v.). See also wrap around. 3. If too many cables are connected together and too many geophone groups are connected, groups at different locations may feed the same channel, producing confusing results.